Merge pull request #6345 from sudo-sturbia:mq/syscalls

PiperOrigin-RevId: 404901660

19 files changed, 1272 insertions, 8 deletions

diff --git a/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go b/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
index 9d7526e47..652ade564 100644
--- a/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
+++ b/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
@@ -74,6 +74,11 @@ func (*DynamicBytesFile) SetStat(context.Context, *vfs.Filesystem, *auth.Credent
 	return linuxerr.EPERM
 }
 
+// Locks returns the file locks for this file.
+func (f *DynamicBytesFile) Locks() *vfs.FileLocks {
+	return &f.locks
+}
+
 // DynamicBytesFD implements vfs.FileDescriptionImpl for an FD backed by a
 // DynamicBytesFile.
 //
diff --git a/pkg/sentry/fsimpl/mqfs/BUILD b/pkg/sentry/fsimpl/mqfs/BUILD
new file mode 100644
index 000000000..332c9b504
--- /dev/null
+++ b/pkg/sentry/fsimpl/mqfs/BUILD
@@ -0,0 +1,41 @@
+load("//tools:defs.bzl", "go_library")
+load("//tools/go_generics:defs.bzl", "go_template_instance")
+
+package(licenses = ["notice"])
+
+go_template_instance(
+    name = "root_inode_refs",
+    out = "root_inode_refs.go",
+    package = "mqfs",
+    prefix = "rootInode",
+    template = "//pkg/refsvfs2:refs_template",
+    types = {
+        "T": "rootInode",
+    },
+)
+
+go_library(
+    name = "mqfs",
+    srcs = [
+        "mqfs.go",
+        "queue.go",
+        "registry.go",
+        "root.go",
+        "root_inode_refs.go",
+    ],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/context",
+        "//pkg/errors/linuxerr",
+        "//pkg/refsvfs2",
+        "//pkg/sentry/fs",
+        "//pkg/sentry/fsimpl/kernfs",
+        "//pkg/sentry/kernel/auth",
+        "//pkg/sentry/kernel/ipc",
+        "//pkg/sentry/kernel/mq",
+        "//pkg/sentry/vfs",
+        "//pkg/usermem",
+        "//pkg/waiter",
+    ],
+)
diff --git a/pkg/sentry/fsimpl/mqfs/mqfs.go b/pkg/sentry/fsimpl/mqfs/mqfs.go
new file mode 100644
index 000000000..c2b53c9d0
--- /dev/null
+++ b/pkg/sentry/fsimpl/mqfs/mqfs.go
@@ -0,0 +1,138 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package mqfs provides a filesystem implementation to back POSIX message
+// queues.
+package mqfs
+
+import (
+	"fmt"
+	"strconv"
+
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/ipc"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/mq"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+const (
+	// Name is the user-visible filesystem name.
+	Name                     = "mqueue"
+	defaultMaxCachedDentries = uint64(1000)
+)
+
+// FilesystemType implements vfs.FilesystemType.
+//
+// +stateify savable
+type FilesystemType struct{}
+
+// Name implements vfs.FilesystemType.Name.
+func (FilesystemType) Name() string {
+	return Name
+}
+
+// Release implements vfs.FilesystemType.Release.
+func (FilesystemType) Release(ctx context.Context) {}
+
+// GetFilesystem implements vfs.FilesystemType.GetFilesystem.
+func (ft FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
+	// mqfs is initialized only once per ipc namespace. Each ipc namespace has
+	// a POSIX message registry with a root dentry, filesystem, and a
+	// disconnected mount. We want the fs to be consistent for all processes in
+	// the same ipc namespace, so instead of creating a new fs and root dentry,
+	// we retreive them using IPCNamespace.PosixQueues and use them.
+
+	i := ipcNamespaceFromContext(ctx)
+	if i == nil {
+		return nil, nil, fmt.Errorf("mqfs.FilesystemType.GetFilesystem: ipc namespace doesn't exist")
+	}
+	defer i.DecRef(ctx)
+
+	registry := i.PosixQueues()
+	if registry == nil {
+		return nil, nil, fmt.Errorf("mqfs.FilesystemType.GetFilesystem: ipc namespace doesn't have a POSIX registry")
+	}
+	impl := registry.Impl().(*RegistryImpl)
+
+	maxCachedDentries, err := maxCachedDentries(ctx, vfs.GenericParseMountOptions(opts.Data))
+	if err != nil {
+		return nil, nil, err
+	}
+	impl.fs.MaxCachedDentries = maxCachedDentries
+
+	impl.fs.VFSFilesystem().IncRef()
+	return impl.fs.VFSFilesystem(), impl.root.VFSDentry(), nil
+}
+
+// maxCachedDentries checks mopts for dentry_cache_limit. If a value is
+// specified, parse it into uint64 and return it. Otherwise, return the default
+// value. An error is returned if a value is found but can't be parsed.
+func maxCachedDentries(ctx context.Context, mopts map[string]string) (_ uint64, err error) {
+	max := defaultMaxCachedDentries
+	if str, ok := mopts["dentry_cache_limit"]; ok {
+		delete(mopts, "dentry_cache_limit")
+		max, err = strconv.ParseUint(str, 10, 64)
+		if err != nil {
+			ctx.Warningf("mqfs.FilesystemType.GetFilesystem: invalid dentry cache limit: dentry_cache_limit=%s", str)
+			return 0, linuxerr.EINVAL
+		}
+	}
+	return max, nil
+}
+
+// filesystem implements kernfs.Filesystem.
+//
+// +stateify savable
+type filesystem struct {
+	kernfs.Filesystem
+	devMinor uint32
+
+	// root is the filesystem's root dentry. Since we take a reference on it in
+	// GetFilesystem, we should release it when the fs is released.
+	root *kernfs.Dentry
+}
+
+// Release implements vfs.FilesystemImpl.Release.
+func (fs *filesystem) Release(ctx context.Context) {
+	fs.Filesystem.VFSFilesystem().VirtualFilesystem().PutAnonBlockDevMinor(fs.devMinor)
+	fs.Filesystem.Release(ctx)
+}
+
+// MountOptions implements vfs.FilesystemImpl.MountOptions.
+func (fs *filesystem) MountOptions() string {
+	return fmt.Sprintf("dentry_cache_limit=%d", fs.MaxCachedDentries)
+}
+
+// ipcNamespace defines functions we need from kernel.IPCNamespace. We redefine
+// ipcNamespace along with ipcNamespaceFromContext to avoid circular dependency
+// with package sentry/kernel.
+type ipcNamespace interface {
+	// PosixQueues returns a POSIX message queue registry.
+	PosixQueues() *mq.Registry
+
+	// DecRef decrements ipcNamespace's number of references.
+	DecRef(ctx context.Context)
+}
+
+// ipcNamespaceFromContext returns the IPC namespace in which ctx is executing.
+// Copied from package sentry/kernel.
+func ipcNamespaceFromContext(ctx context.Context) ipcNamespace {
+	if v := ctx.Value(ipc.CtxIPCNamespace); v != nil {
+		return v.(ipcNamespace)
+	}
+	return nil
+}
diff --git a/pkg/sentry/fsimpl/mqfs/queue.go b/pkg/sentry/fsimpl/mqfs/queue.go
new file mode 100644
index 000000000..933dbc6ed
--- /dev/null
+++ b/pkg/sentry/fsimpl/mqfs/queue.go
@@ -0,0 +1,145 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mqfs
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/mq"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/usermem"
+	"gvisor.dev/gvisor/pkg/waiter"
+)
+
+// queueInode represents an inode for a message queue (/dev/mqueue/[name]).
+//
+// +stateify savable
+type queueInode struct {
+	kernfs.DynamicBytesFile
+
+	// queue is the message queue backing this inode.
+	queue *mq.Queue
+}
+
+var _ kernfs.Inode = (*queueInode)(nil)
+
+// newQueueInode returns a new, initialized queueInode.
+func (fs *filesystem) newQueueInode(ctx context.Context, creds *auth.Credentials, q *mq.Queue, perm linux.FileMode) kernfs.Inode {
+	inode := &queueInode{queue: q}
+	inode.Init(ctx, creds, linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), q, perm)
+	return inode
+}
+
+// Keep implements kernfs.Inode.Keep.
+func (q *queueInode) Keep() bool {
+	// Return true so that the fs keeps newly created dentries. This is done
+	// because inodes returned by root.Lookup are not temporary, they exist
+	// in the fs, and refer to message queues.
+	return true
+}
+
+// queueFD implements vfs.FileDescriptionImpl for FD backed by a POSIX message
+// queue. It's mostly similar to DynamicBytesFD, but implements more operations.
+//
+// +stateify savable
+type queueFD struct {
+	vfs.FileDescriptionDefaultImpl
+	vfs.DynamicBytesFileDescriptionImpl
+	vfs.LockFD
+
+	vfsfd vfs.FileDescription
+	inode kernfs.Inode
+
+	// queue is a view into the queue backing this fd.
+	queue mq.View
+}
+
+// Init initializes a queueFD. Mostly copied from DynamicBytesFD.Init, but uses
+// the queueFD as FileDescriptionImpl.
+func (fd *queueFD) Init(m *vfs.Mount, d *kernfs.Dentry, data vfs.DynamicBytesSource, locks *vfs.FileLocks, flags uint32) error {
+	fd.LockFD.Init(locks)
+	if err := fd.vfsfd.Init(fd, flags, m, d.VFSDentry(), &vfs.FileDescriptionOptions{}); err != nil {
+		return err
+	}
+	fd.inode = d.Inode()
+	fd.SetDataSource(data)
+	return nil
+}
+
+// Seek implements vfs.FileDescriptionImpl.Seek.
+func (fd *queueFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
+	return fd.DynamicBytesFileDescriptionImpl.Seek(ctx, offset, whence)
+}
+
+// Read implements vfs.FileDescriptionImpl.Read.
+func (fd *queueFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+	return fd.DynamicBytesFileDescriptionImpl.Read(ctx, dst, opts)
+}
+
+// PRead implements vfs.FileDescriptionImpl.PRead.
+func (fd *queueFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
+	return fd.DynamicBytesFileDescriptionImpl.PRead(ctx, dst, offset, opts)
+}
+
+// Write implements vfs.FileDescriptionImpl.Write.
+func (fd *queueFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
+	return fd.DynamicBytesFileDescriptionImpl.Write(ctx, src, opts)
+}
+
+// PWrite implements vfs.FileDescriptionImpl.PWrite.
+func (fd *queueFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+	return fd.DynamicBytesFileDescriptionImpl.PWrite(ctx, src, offset, opts)
+}
+
+// Release implements vfs.FileDescriptionImpl.Release.
+func (fd *queueFD) Release(context.Context) {}
+
+// Stat implements vfs.FileDescriptionImpl.Stat.
+func (fd *queueFD) Stat(ctx context.Context, opts vfs.StatOptions) (linux.Statx, error) {
+	fs := fd.vfsfd.VirtualDentry().Mount().Filesystem()
+	return fd.inode.Stat(ctx, fs, opts)
+}
+
+// SetStat implements vfs.FileDescriptionImpl.SetStat.
+func (fd *queueFD) SetStat(context.Context, vfs.SetStatOptions) error {
+	// DynamicBytesFiles are immutable.
+	return linuxerr.EPERM
+}
+
+// OnClose implements FileDescriptionImpl.OnClose similar to
+// ipc/mqueue.c::mqueue_flush_file.
+func (fd *queueFD) OnClose(ctx context.Context) error {
+	fd.queue.Flush(ctx)
+	return nil
+}
+
+// Readiness implements waiter.Waitable.Readiness similar to
+// ipc/mqueue.c::mqueue_poll_file.
+func (fd *queueFD) Readiness(mask waiter.EventMask) waiter.EventMask {
+	return fd.queue.Readiness(mask)
+}
+
+// EventRegister implements Waitable.EventRegister.
+func (fd *queueFD) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
+	fd.queue.EventRegister(e, mask)
+}
+
+// EventUnregister implements Waitable.EventUnregister.
+func (fd *queueFD) EventUnregister(e *waiter.Entry) {
+	fd.queue.EventUnregister(e)
+}
diff --git a/pkg/sentry/fsimpl/mqfs/registry.go b/pkg/sentry/fsimpl/mqfs/registry.go
new file mode 100644
index 000000000..c8fbe4d33
--- /dev/null
+++ b/pkg/sentry/fsimpl/mqfs/registry.go
@@ -0,0 +1,176 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mqfs
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/mq"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+// RegistryImpl implements mq.RegistryImpl. It implements the interface using
+// the message queue filesystem, and is provided to mq.Registry at
+// initialization.
+//
+// RegistryImpl is not thread-safe, so it is the responsibility of the user
+// (the containing mq.Registry) to protect using a lock.
+//
+// +stateify savable
+type RegistryImpl struct {
+	// root is the root dentry of the mq filesystem. Its main usage is to
+	// retreive the root inode, which we use to add, remove, and lookup message
+	// queues.
+	//
+	// We hold a reference on root and release when the registry is destroyed.
+	root *kernfs.Dentry
+
+	// fs is the filesystem backing this registry, used mainly to initialize
+	// new inodes.
+	fs *filesystem
+
+	// mount is the mount point used for this filesystem.
+	mount *vfs.Mount
+}
+
+// NewRegistryImpl returns a new, initialized RegistryImpl, and takes a
+// reference on root.
+func NewRegistryImpl(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials) (*RegistryImpl, error) {
+	devMinor, err := vfsObj.GetAnonBlockDevMinor()
+	if err != nil {
+		return nil, err
+	}
+
+	var dentry kernfs.Dentry
+	fs := &filesystem{
+		devMinor: devMinor,
+		root:     &dentry,
+	}
+	fs.VFSFilesystem().Init(vfsObj, &FilesystemType{}, fs)
+	vfsfs := fs.VFSFilesystem()
+
+	dentry.InitRoot(&fs.Filesystem, fs.newRootInode(ctx, creds))
+	defer vfsfs.DecRef(ctx) // NewDisconnectedMount will obtain a ref on success.
+
+	mount, err := vfsObj.NewDisconnectedMount(vfsfs, dentry.VFSDentry(), &vfs.MountOptions{})
+	if err != nil {
+		return nil, err
+	}
+
+	return &RegistryImpl{
+		root:  &dentry,
+		fs:    fs,
+		mount: mount,
+	}, nil
+}
+
+// Get implements mq.RegistryImpl.Get.
+func (r *RegistryImpl) Get(ctx context.Context, name string, access mq.AccessType, block bool, flags uint32) (*vfs.FileDescription, bool, error) {
+	inode, err := r.lookup(ctx, name)
+	if err != nil {
+		return nil, false, nil
+	}
+
+	qInode := inode.(*queueInode)
+	if !qInode.queue.HasPermissions(auth.CredentialsFromContext(ctx), perm(access)) {
+		// "The queue exists, but the caller does not have permission to
+		//  open it in the specified mode."
+		return nil, false, linuxerr.EACCES
+	}
+
+	fd, err := r.newFD(qInode.queue, qInode, access, block, flags)
+	if err != nil {
+		return nil, false, err
+	}
+	return fd, true, nil
+}
+
+// New implements mq.RegistryImpl.New.
+func (r *RegistryImpl) New(ctx context.Context, name string, q *mq.Queue, access mq.AccessType, block bool, perm linux.FileMode, flags uint32) (*vfs.FileDescription, error) {
+	root := r.root.Inode().(*rootInode)
+	qInode := r.fs.newQueueInode(ctx, auth.CredentialsFromContext(ctx), q, perm).(*queueInode)
+	err := root.Insert(name, qInode)
+	if err != nil {
+		return nil, err
+	}
+	return r.newFD(q, qInode, access, block, flags)
+}
+
+// Unlink implements mq.RegistryImpl.Unlink.
+func (r *RegistryImpl) Unlink(ctx context.Context, name string) error {
+	creds := auth.CredentialsFromContext(ctx)
+	if err := r.root.Inode().CheckPermissions(ctx, creds, vfs.MayWrite|vfs.MayExec); err != nil {
+		return err
+	}
+
+	root := r.root.Inode().(*rootInode)
+	inode, err := r.lookup(ctx, name)
+	if err != nil {
+		return err
+	}
+	return root.Unlink(ctx, name, inode)
+}
+
+// Destroy implements mq.RegistryImpl.Destroy.
+func (r *RegistryImpl) Destroy(ctx context.Context) {
+	r.root.DecRef(ctx)
+	r.mount.DecRef(ctx)
+}
+
+// lookup retreives a kernfs.Inode using a name.
+func (r *RegistryImpl) lookup(ctx context.Context, name string) (kernfs.Inode, error) {
+	inode := r.root.Inode().(*rootInode)
+	lookup, err := inode.Lookup(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+	return lookup, nil
+}
+
+// newFD returns a new file description created using the given queue and inode.
+func (r *RegistryImpl) newFD(q *mq.Queue, inode *queueInode, access mq.AccessType, block bool, flags uint32) (*vfs.FileDescription, error) {
+	view, err := mq.NewView(q, access, block)
+	if err != nil {
+		return nil, err
+	}
+
+	var dentry kernfs.Dentry
+	dentry.Init(&r.fs.Filesystem, inode)
+
+	fd := &queueFD{queue: view}
+	err = fd.Init(r.mount, &dentry, inode.queue, inode.Locks(), flags)
+	if err != nil {
+		return nil, err
+	}
+	return &fd.vfsfd, nil
+}
+
+// perm returns a permission mask created using given flags.
+func perm(access mq.AccessType) fs.PermMask {
+	switch access {
+	case mq.ReadWrite:
+		return fs.PermMask{Read: true, Write: true}
+	case mq.WriteOnly:
+		return fs.PermMask{Write: true}
+	case mq.ReadOnly:
+		return fs.PermMask{Read: true}
+	default:
+		return fs.PermMask{} // Can't happen, see NewView.
+	}
+}
diff --git a/pkg/sentry/fsimpl/mqfs/root.go b/pkg/sentry/fsimpl/mqfs/root.go
new file mode 100644
index 000000000..37b5749fb
--- /dev/null
+++ b/pkg/sentry/fsimpl/mqfs/root.go
@@ -0,0 +1,89 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mqfs
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+// rootInode represents inode for filesystem's root directory (/dev/mqueue).
+//
+// +stateify savable
+type rootInode struct {
+	rootInodeRefs
+	kernfs.InodeAlwaysValid
+	kernfs.InodeAttrs
+	kernfs.InodeDirectoryNoNewChildren
+	kernfs.InodeNotSymlink
+	kernfs.InodeTemporary
+	kernfs.OrderedChildren
+	implStatFS
+
+	locks vfs.FileLocks
+}
+
+var _ kernfs.Inode = (*rootInode)(nil)
+
+// newRootInode returns a new, initialized rootInode.
+func (fs *filesystem) newRootInode(ctx context.Context, creds *auth.Credentials) kernfs.Inode {
+	inode := &rootInode{}
+	inode.InodeAttrs.Init(ctx, creds, linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), linux.ModeDirectory|linux.FileMode(0555))
+	inode.OrderedChildren.Init(kernfs.OrderedChildrenOptions{Writable: true})
+	inode.InitRefs()
+	return inode
+}
+
+// Open implements kernfs.Inode.Open.
+func (i *rootInode) Open(ctx context.Context, rp *vfs.ResolvingPath, d *kernfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
+	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), d, &i.OrderedChildren, &i.locks, &opts, kernfs.GenericDirectoryFDOptions{
+		SeekEnd: kernfs.SeekEndZero,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return fd.VFSFileDescription(), nil
+}
+
+// DecRef implements kernfs.Inode.DecRef.
+func (i *rootInode) DecRef(ctx context.Context) {
+	i.rootInodeRefs.DecRef(func() { i.Destroy(ctx) })
+}
+
+// Rename implements Inode.Rename and overrides OrderedChildren.Rename. mqueue
+// filesystem allows files to be unlinked, but not renamed.
+func (i *rootInode) Rename(ctx context.Context, oldname, newname string, child, dstDir kernfs.Inode) error {
+	return linuxerr.EPERM
+}
+
+// SetStat implements kernfs.Inode.SetStat not allowing inode attributes to be changed.
+func (*rootInode) SetStat(context.Context, *vfs.Filesystem, *auth.Credentials, vfs.SetStatOptions) error {
+	return linuxerr.EPERM
+}
+
+// implStatFS provides an implementation of kernfs.Inode.StatFS for message
+// queues to be embedded in inodes.
+//
+// +stateify savable
+type implStatFS struct{}
+
+// StatFS implements kernfs.Inode.StatFS.
+func (*implStatFS) StatFS(context.Context, *vfs.Filesystem) (linux.Statfs, error) {
+	return vfs.GenericStatFS(linux.MQUEUE_MAGIC), nil
+}
diff --git a/pkg/sentry/kernel/BUILD b/pkg/sentry/kernel/BUILD
index 53a21e1e2..f3f16eb7a 100644
--- a/pkg/sentry/kernel/BUILD
+++ b/pkg/sentry/kernel/BUILD
@@ -248,6 +248,7 @@ go_library(
         "//pkg/sentry/fs/timerfd",
         "//pkg/sentry/fsbridge",
         "//pkg/sentry/fsimpl/kernfs",
+        "//pkg/sentry/fsimpl/mqfs",
         "//pkg/sentry/fsimpl/pipefs",
         "//pkg/sentry/fsimpl/sockfs",
         "//pkg/sentry/fsimpl/timerfd",
@@ -256,6 +257,8 @@ go_library(
         "//pkg/sentry/inet",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/futex",
+        "//pkg/sentry/kernel/ipc",
+        "//pkg/sentry/kernel/mq",
         "//pkg/sentry/kernel/msgqueue",
         "//pkg/sentry/kernel/sched",
         "//pkg/sentry/kernel/semaphore",
diff --git a/pkg/sentry/kernel/context.go b/pkg/sentry/kernel/context.go
index a8596410f..7e11c6580 100644
--- a/pkg/sentry/kernel/context.go
+++ b/pkg/sentry/kernel/context.go
@@ -16,6 +16,7 @@ package kernel
 
 import (
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/ipc"
 )
 
 // contextID is the kernel package's type for context.Context.Value keys.
@@ -37,9 +38,6 @@ const (
 
 	// CtxUTSNamespace is a Context.Value key for a UTSNamespace.
 	CtxUTSNamespace
-
-	// CtxIPCNamespace is a Context.Value key for a IPCNamespace.
-	CtxIPCNamespace
 )
 
 // ContextCanTrace returns true if ctx is permitted to trace t, in the same sense
@@ -82,7 +80,7 @@ func UTSNamespaceFromContext(ctx context.Context) *UTSNamespace {
 // or nil if there is no such IPC namespace. It takes a reference on the
 // namespace.
 func IPCNamespaceFromContext(ctx context.Context) *IPCNamespace {
-	if v := ctx.Value(CtxIPCNamespace); v != nil {
+	if v := ctx.Value(ipc.CtxIPCNamespace); v != nil {
 		return v.(*IPCNamespace)
 	}
 	return nil
diff --git a/pkg/sentry/kernel/ipc/BUILD b/pkg/sentry/kernel/ipc/BUILD
index e42a94e15..bb5cf1c17 100644
--- a/pkg/sentry/kernel/ipc/BUILD
+++ b/pkg/sentry/kernel/ipc/BUILD
@@ -5,6 +5,7 @@ package(licenses = ["notice"])
 go_library(
     name = "ipc",
     srcs = [
+        "ns.go",
         "object.go",
         "registry.go",
     ],
diff --git a/pkg/sentry/kernel/ipc/ns.go b/pkg/sentry/kernel/ipc/ns.go
new file mode 100644
index 000000000..220c9eafb
--- /dev/null
+++ b/pkg/sentry/kernel/ipc/ns.go
@@ -0,0 +1,22 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ipc
+
+type contextID int
+
+// CtxIPCNamespace is the context.Value key used to retreive an IPC namespace.
+// We define it here because it's needed in several packages, and is not
+// possible to use otherwise without causing a circular depenedency.
+const CtxIPCNamespace contextID = iota
diff --git a/pkg/sentry/kernel/ipc_namespace.go b/pkg/sentry/kernel/ipc_namespace.go
index 0b101b1bb..50b4e015e 100644
--- a/pkg/sentry/kernel/ipc_namespace.go
+++ b/pkg/sentry/kernel/ipc_namespace.go
@@ -15,11 +15,16 @@
 package kernel
 
 import (
+	"fmt"
+
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/mqfs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/mq"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/msgqueue"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/semaphore"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/shm"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
 )
 
 // IPCNamespace represents an IPC namespace.
@@ -31,9 +36,17 @@ type IPCNamespace struct {
 	// User namespace which owns this IPC namespace. Immutable.
 	userNS *auth.UserNamespace
 
+	// System V utilities.
 	queues     *msgqueue.Registry
 	semaphores *semaphore.Registry
 	shms       *shm.Registry
+
+	// posixQueues is a POSIX message queue registry.
+	//
+	// posixQueues is somewhat equivelant to Linux's ipc_namespace.mq_mnt.
+	// Unlike SysV utilities, mq.Registry is not map-based, but is backed by
+	// a virtual filesystem.
+	posixQueues *mq.Registry
 }
 
 // NewIPCNamespace creates a new IPC namespace.
@@ -63,10 +76,35 @@ func (i *IPCNamespace) ShmRegistry() *shm.Registry {
 	return i.shms
 }
 
+// InitPosixQueues creates a new POSIX queue registry, and returns an error if
+// the registry was previously initialized.
+func (i *IPCNamespace) InitPosixQueues(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials) error {
+	if i.posixQueues != nil {
+		return fmt.Errorf("IPCNamespace.InitPosixQueues: already initialized")
+	}
+
+	impl, err := mqfs.NewRegistryImpl(ctx, vfsObj, creds)
+	if err != nil {
+		return err
+	}
+	i.posixQueues = mq.NewRegistry(i.userNS, impl)
+	return nil
+}
+
+// PosixQueues returns the posix message queue registry for this namespace.
+//
+// Precondition: i.InitPosixQueues must have been called.
+func (i *IPCNamespace) PosixQueues() *mq.Registry {
+	return i.posixQueues
+}
+
 // DecRef implements refsvfs2.RefCounter.DecRef.
 func (i *IPCNamespace) DecRef(ctx context.Context) {
 	i.IPCNamespaceRefs.DecRef(func() {
 		i.shms.Release(ctx)
+		if i.posixQueues != nil {
+			i.posixQueues.Destroy(ctx)
+		}
 	})
 }
 
diff --git a/pkg/sentry/kernel/kernel.go b/pkg/sentry/kernel/kernel.go
index 5dc821a48..d4851ccda 100644
--- a/pkg/sentry/kernel/kernel.go
+++ b/pkg/sentry/kernel/kernel.go
@@ -58,6 +58,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/futex"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/ipc"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/sched"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
@@ -407,6 +408,11 @@ func (k *Kernel) Init(args InitKernelArgs) error {
 			return fmt.Errorf("failed to initialize VFS: %v", err)
 		}
 
+		err := k.rootIPCNamespace.InitPosixQueues(ctx, &k.vfs, auth.CredentialsFromContext(ctx))
+		if err != nil {
+			return fmt.Errorf("failed to create mqfs filesystem: %v", err)
+		}
+
 		pipeFilesystem, err := pipefs.NewFilesystem(&k.vfs)
 		if err != nil {
 			return fmt.Errorf("failed to create pipefs filesystem: %v", err)
@@ -837,7 +843,7 @@ func (ctx *createProcessContext) Value(key interface{}) interface{} {
 		return ctx.args.PIDNamespace
 	case CtxUTSNamespace:
 		return ctx.args.UTSNamespace
-	case CtxIPCNamespace:
+	case ipc.CtxIPCNamespace:
 		ipcns := ctx.args.IPCNamespace
 		ipcns.IncRef()
 		return ipcns
@@ -1665,7 +1671,7 @@ func (ctx supervisorContext) Value(key interface{}) interface{} {
 		return ctx.k.tasks.Root
 	case CtxUTSNamespace:
 		return ctx.k.rootUTSNamespace
-	case CtxIPCNamespace:
+	case ipc.CtxIPCNamespace:
 		ipcns := ctx.k.rootIPCNamespace
 		ipcns.IncRef()
 		return ipcns
diff --git a/pkg/sentry/kernel/mq/BUILD b/pkg/sentry/kernel/mq/BUILD
new file mode 100644
index 000000000..fefac3ba5
--- /dev/null
+++ b/pkg/sentry/kernel/mq/BUILD
@@ -0,0 +1,35 @@
+load("//tools:defs.bzl", "go_library")
+load("//tools/go_generics:defs.bzl", "go_template_instance")
+
+package(licenses = ["notice"])
+
+go_template_instance(
+    name = "message_list",
+    out = "message_list.go",
+    package = "mq",
+    prefix = "msg",
+    template = "//pkg/ilist:generic_list",
+    types = {
+        "Element": "*Message",
+        "Linker": "*Message",
+    },
+)
+
+go_library(
+    name = "mq",
+    srcs = [
+        "message_list.go",
+        "mq.go",
+    ],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/context",
+        "//pkg/errors/linuxerr",
+        "//pkg/sentry/fs",
+        "//pkg/sentry/kernel/auth",
+        "//pkg/sentry/vfs",
+        "//pkg/sync",
+        "//pkg/waiter",
+    ],
+)
diff --git a/pkg/sentry/kernel/mq/mq.go b/pkg/sentry/kernel/mq/mq.go
new file mode 100644
index 000000000..50ca6d34a
--- /dev/null
+++ b/pkg/sentry/kernel/mq/mq.go
@@ -0,0 +1,457 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package mq provides an implementation for POSIX message queues.
+package mq
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
+	"gvisor.dev/gvisor/pkg/waiter"
+)
+
+// AccessType is the access type passed to mq_open.
+type AccessType int
+
+// Possible access types.
+const (
+	ReadOnly AccessType = iota
+	WriteOnly
+	ReadWrite
+)
+
+// MaxName is the maximum size for a queue name.
+const MaxName = 255
+
+const (
+	maxPriority = linux.MQ_PRIO_MAX - 1 // Highest possible message priority.
+
+	maxQueuesDefault = linux.DFLT_QUEUESMAX // Default max number of queues.
+
+	maxMsgDefault   = linux.DFLT_MSG    // Default max number of messages per queue.
+	maxMsgMin       = linux.MIN_MSGMAX  // Min value for max number of messages per queue.
+	maxMsgLimit     = linux.DFLT_MSGMAX // Limit for max number of messages per queue.
+	maxMsgHardLimit = linux.HARD_MSGMAX // Hard limit for max number of messages per queue.
+
+	msgSizeDefault   = linux.DFLT_MSGSIZE    // Default max message size.
+	msgSizeMin       = linux.MIN_MSGSIZEMAX  // Min value for max message size.
+	msgSizeLimit     = linux.DFLT_MSGSIZEMAX // Limit for max message size.
+	msgSizeHardLimit = linux.HARD_MSGSIZEMAX // Hard limit for max message size.
+)
+
+// Registry is a POSIX message queue registry.
+//
+// Unlike SysV utilities, Registry is not map-based. It uses a provided
+// RegistryImpl backed by a virtual filesystem to implement registry operations.
+//
+// +stateify savable
+type Registry struct {
+	// userNS is the user namespace containing this registry. Immutable.
+	userNS *auth.UserNamespace
+
+	// mu protects all fields below.
+	mu sync.Mutex `state:"nosave"`
+
+	// impl is an implementation of several message queue utilities needed by
+	// the registry. impl should be provided by mqfs.
+	impl RegistryImpl
+}
+
+// RegistryImpl defines utilities needed by a Registry to provide actual
+// registry implementation. It works mainly as an abstraction layer used by
+// Registry to avoid dealing directly with the filesystem. RegistryImpl should
+// be implemented by mqfs and provided to Registry at initialization.
+type RegistryImpl interface {
+	// Get searchs for a queue with the given name, if it exists, the queue is
+	// used to create a new FD, return it and return true. If the queue  doesn't
+	// exist, return false and no error. An error is returned if creation fails.
+	Get(ctx context.Context, name string, access AccessType, block bool, flags uint32) (*vfs.FileDescription, bool, error)
+
+	// New creates a new inode and file description using the given queue,
+	// inserts the inode into the filesystem tree using the given name, and
+	// returns the file description. An error is returned if creation fails, or
+	// if the name already exists.
+	New(ctx context.Context, name string, q *Queue, access AccessType, block bool, perm linux.FileMode, flags uint32) (*vfs.FileDescription, error)
+
+	// Unlink removes the queue with given name from the registry, and returns
+	// an error if the name doesn't exist.
+	Unlink(ctx context.Context, name string) error
+
+	// Destroy destroys the registry.
+	Destroy(context.Context)
+}
+
+// NewRegistry returns a new, initialized message queue registry. NewRegistry
+// should be called when a new message queue filesystem is created, once per
+// IPCNamespace.
+func NewRegistry(userNS *auth.UserNamespace, impl RegistryImpl) *Registry {
+	return &Registry{
+		userNS: userNS,
+		impl:   impl,
+	}
+}
+
+// OpenOpts holds the options passed to FindOrCreate.
+type OpenOpts struct {
+	Name      string
+	Access    AccessType
+	Create    bool
+	Exclusive bool
+	Block     bool
+}
+
+// FindOrCreate creates a new POSIX message queue or opens an existing queue.
+// See mq_open(2).
+func (r *Registry) FindOrCreate(ctx context.Context, opts OpenOpts, perm linux.FileMode, attr *linux.MqAttr) (*vfs.FileDescription, error) {
+	// mq_overview(7) mentions that: "Each message queue is identified by a name
+	// of the form '/somename'", but the mq_open(3) man pages mention:
+	//   "The mq_open() library function is implemented on top of a system call
+	//    of the same name.  The library function performs the check that the
+	//    name starts with a slash (/), giving the EINVAL error if it does not.
+	//    The kernel system call expects name to contain no preceding slash, so
+	//    the C library function passes name without the preceding slash (i.e.,
+	//    name+1) to the system call."
+	// So we don't need to check it.
+
+	if len(opts.Name) == 0 {
+		return nil, linuxerr.ENOENT
+	}
+	if len(opts.Name) > MaxName {
+		return nil, linuxerr.ENAMETOOLONG
+	}
+	if strings.ContainsRune(opts.Name, '/') {
+		return nil, linuxerr.EACCES
+	}
+	if opts.Name == "." || opts.Name == ".." {
+		return nil, linuxerr.EINVAL
+	}
+
+	// Construct status flags.
+	var flags uint32
+	if opts.Block {
+		flags = linux.O_NONBLOCK
+	}
+	switch opts.Access {
+	case ReadOnly:
+		flags = flags | linux.O_RDONLY
+	case WriteOnly:
+		flags = flags | linux.O_WRONLY
+	case ReadWrite:
+		flags = flags | linux.O_RDWR
+	}
+
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	fd, ok, err := r.impl.Get(ctx, opts.Name, opts.Access, opts.Block, flags)
+	if err != nil {
+		return nil, err
+	}
+
+	if ok {
+		if opts.Create && opts.Exclusive {
+			// "Both O_CREAT and O_EXCL were specified in oflag, but a queue
+			//  with this name already exists."
+			return nil, linuxerr.EEXIST
+		}
+		return fd, nil
+	}
+
+	if !opts.Create {
+		// "The O_CREAT flag was not specified in oflag, and no queue with this name
+		//  exists."
+		return nil, linuxerr.ENOENT
+	}
+
+	q, err := r.newQueueLocked(auth.CredentialsFromContext(ctx), fs.FileOwnerFromContext(ctx), fs.FilePermsFromMode(perm), attr)
+	if err != nil {
+		return nil, err
+	}
+	return r.impl.New(ctx, opts.Name, q, opts.Access, opts.Block, perm, flags)
+}
+
+// newQueueLocked creates a new queue using the given attributes. If attr is nil
+// return a queue with default values, otherwise use attr to create a new queue,
+// and return an error if attributes are invalid.
+func (r *Registry) newQueueLocked(creds *auth.Credentials, owner fs.FileOwner, perms fs.FilePermissions, attr *linux.MqAttr) (*Queue, error) {
+	if attr == nil {
+		return &Queue{
+			owner:           owner,
+			perms:           perms,
+			maxMessageCount: int64(maxMsgDefault),
+			maxMessageSize:  uint64(msgSizeDefault),
+		}, nil
+	}
+
+	// "O_CREAT was specified in oflag, and attr was not NULL, but
+	//  attr->mq_maxmsg or attr->mq_msqsize was invalid.  Both of these fields
+	//  these fields must be greater than zero.  In a process that is
+	//  unprivileged (does not have the CAP_SYS_RESOURCE capability),
+	//  attr->mq_maxmsg must be less than or equal to the msg_max limit, and
+	//  attr->mq_msgsize must be less than or equal to the msgsize_max limit.
+	//  In addition, even in a privileged process, attr->mq_maxmsg cannot
+	//  exceed the HARD_MAX limit." - man mq_open(3).
+	if attr.MqMaxmsg <= 0 || attr.MqMsgsize <= 0 {
+		return nil, linuxerr.EINVAL
+	}
+
+	if attr.MqMaxmsg > maxMsgHardLimit || (!creds.HasCapabilityIn(linux.CAP_SYS_RESOURCE, r.userNS) && (attr.MqMaxmsg > maxMsgLimit || attr.MqMsgsize > msgSizeLimit)) {
+		return nil, linuxerr.EINVAL
+	}
+
+	return &Queue{
+		owner:           owner,
+		perms:           perms,
+		maxMessageCount: attr.MqMaxmsg,
+		maxMessageSize:  uint64(attr.MqMsgsize),
+	}, nil
+}
+
+// Remove removes the queue with the given name from the registry. See
+// mq_unlink(2).
+func (r *Registry) Remove(ctx context.Context, name string) error {
+	if len(name) > MaxName {
+		return linuxerr.ENAMETOOLONG
+	}
+
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	return r.impl.Unlink(ctx, name)
+}
+
+// Destroy destroys the registry and releases all held references.
+func (r *Registry) Destroy(ctx context.Context) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.impl.Destroy(ctx)
+}
+
+// Impl returns RegistryImpl inside r.
+func (r *Registry) Impl() RegistryImpl {
+	return r.impl
+}
+
+// Queue represents a POSIX message queue.
+//
+// +stateify savable
+type Queue struct {
+	// owner is the registry's owner. Immutable.
+	owner fs.FileOwner
+
+	// perms is the registry's access permissions. Immutable.
+	perms fs.FilePermissions
+
+	// mu protects all the fields below.
+	mu sync.Mutex `state:"nosave"`
+
+	// senders is a queue of currently blocked senders. Senders are notified
+	// when space isi available in the queue for a new message.
+	senders waiter.Queue
+
+	// receivers is a queue of currently blocked receivers. Receivers are
+	// notified when a new message is inserted in the queue.
+	receivers waiter.Queue
+
+	// messages is a list of messages currently in the queue.
+	messages msgList
+
+	// subscriber represents a task registered to receive async notification
+	// from this queue.
+	subscriber *Subscriber
+
+	// messageCount is the number of messages currently in the queue.
+	messageCount int64
+
+	// maxMessageCount is the maximum number of messages that the queue can
+	// hold.
+	maxMessageCount int64
+
+	// maxMessageSize is the maximum size of a message held by the queue.
+	maxMessageSize uint64
+
+	// byteCount is the number of bytes of data in all messages in the queue.
+	byteCount uint64
+}
+
+// View is a view into a message queue. Views should only be used in file
+// descriptions, but not inodes, because we use inodes to retreive the actual
+// queue, and only FDs are responsible for providing user functionality.
+type View interface {
+	// TODO: Add Send and Receive when mq_timedsend(2) and mq_timedreceive(2)
+	// are implemented.
+
+	// Flush checks if the calling process has attached a notification request
+	// to this queue, if yes, then the request is removed, and another process
+	// can attach a request.
+	Flush(ctx context.Context)
+
+	waiter.Waitable
+}
+
+// ReaderWriter provides a send and receive view into a queue.
+type ReaderWriter struct {
+	*Queue
+
+	block bool
+}
+
+// Reader provides a send-only view into a queue.
+type Reader struct {
+	*Queue
+
+	block bool
+}
+
+// Writer provides a receive-only view into a queue.
+type Writer struct {
+	*Queue
+
+	block bool
+}
+
+// NewView creates a new view into a queue and returns it.
+func NewView(q *Queue, access AccessType, block bool) (View, error) {
+	switch access {
+	case ReadWrite:
+		return ReaderWriter{Queue: q, block: block}, nil
+	case WriteOnly:
+		return Writer{Queue: q, block: block}, nil
+	case ReadOnly:
+		return Reader{Queue: q, block: block}, nil
+	default:
+		// This case can't happen, due to O_RDONLY flag being 0 and O_WRONLY
+		// being 1, so one of them must be true.
+		return nil, linuxerr.EINVAL
+	}
+}
+
+// Message holds a message exchanged through a Queue via mq_timedsend(2) and
+// mq_timedreceive(2), and additional info relating to the message.
+//
+// +stateify savable
+type Message struct {
+	msgEntry
+
+	// Text is the message's sent content.
+	Text string
+
+	// Size is the message's size in bytes.
+	Size uint64
+
+	// Priority is the message's priority.
+	Priority uint32
+}
+
+// Subscriber represents a task registered for async notification from a Queue.
+//
+// +stateify savable
+type Subscriber struct {
+	// TODO: Add fields when mq_notify(2) is implemented.
+
+	// pid is the PID of the registered task.
+	pid int32
+}
+
+// Generate implements vfs.DynamicBytesSource.Generate. Queue is used as a
+// DynamicBytesSource for mqfs's queueInode.
+func (q *Queue) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+
+	var (
+		pid       int32
+		method    int
+		sigNumber int
+	)
+	if q.subscriber != nil {
+		pid = q.subscriber.pid
+		// TODO: add method and sigNumber when mq_notify(2) is implemented.
+	}
+
+	buf.WriteString(
+		fmt.Sprintf("QSIZE:%-10d NOTIFY:%-5d SIGNO:%-5d NOTIFY_PID:%-6d\n",
+			q.byteCount, method, sigNumber, pid),
+	)
+	return nil
+}
+
+// Flush implements View.Flush.
+func (q *Queue) Flush(ctx context.Context) {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+
+	pid, ok := context.ThreadGroupIDFromContext(ctx)
+	if ok {
+		if q.subscriber != nil && pid == q.subscriber.pid {
+			q.subscriber = nil
+		}
+	}
+}
+
+// Readiness implements Waitable.Readiness.
+func (q *Queue) Readiness(mask waiter.EventMask) waiter.EventMask {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+
+	events := waiter.EventMask(0)
+	if q.messageCount > 0 {
+		events |= waiter.ReadableEvents
+	}
+	if q.messageCount < q.maxMessageCount {
+		events |= waiter.WritableEvents
+	}
+	return events & mask
+}
+
+// EventRegister implements Waitable.EventRegister.
+func (q *Queue) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+
+	if mask&waiter.WritableEvents != 0 {
+		q.senders.EventRegister(e, waiter.EventOut)
+	}
+	if mask&waiter.ReadableEvents != 0 {
+		q.receivers.EventRegister(e, waiter.EventIn)
+	}
+}
+
+// EventUnregister implements Waitable.EventUnregister.
+func (q *Queue) EventUnregister(e *waiter.Entry) {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+
+	q.senders.EventUnregister(e)
+	q.receivers.EventUnregister(e)
+}
+
+// HasPermissions returns true if the given credentials meet the access
+// permissions required by the queue.
+func (q *Queue) HasPermissions(creds *auth.Credentials, req fs.PermMask) bool {
+	p := q.perms.Other
+	if q.owner.UID == creds.EffectiveKUID {
+		p = q.perms.User
+	} else if creds.InGroup(q.owner.GID) {
+		p = q.perms.Group
+	}
+	return p.SupersetOf(req)
+}
diff --git a/pkg/sentry/kernel/task_clone.go b/pkg/sentry/kernel/task_clone.go
index a6d8fb163..69a3227f0 100644
--- a/pkg/sentry/kernel/task_clone.go
+++ b/pkg/sentry/kernel/task_clone.go
@@ -103,6 +103,9 @@ func (t *Task) Clone(args *linux.CloneArgs) (ThreadID, *SyscallControl, error) {
 	ipcns := t.IPCNamespace()
 	if args.Flags&linux.CLONE_NEWIPC != 0 {
 		ipcns = NewIPCNamespace(userns)
+		if VFS2Enabled {
+			ipcns.InitPosixQueues(t, t.k.VFS(), creds)
+		}
 	} else {
 		ipcns.IncRef()
 	}
@@ -464,6 +467,9 @@ func (t *Task) Unshare(flags int32) error {
 		// namespace"
 		t.ipcns.DecRef(t)
 		t.ipcns = NewIPCNamespace(creds.UserNamespace)
+		if VFS2Enabled {
+			t.ipcns.InitPosixQueues(t, t.k.VFS(), creds)
+		}
 	}
 	var oldFDTable *FDTable
 	if flags&linux.CLONE_FILES != 0 {
diff --git a/pkg/sentry/kernel/task_context.go b/pkg/sentry/kernel/task_context.go
index c82d9e82b..cb9bcd7c0 100644
--- a/pkg/sentry/kernel/task_context.go
+++ b/pkg/sentry/kernel/task_context.go
@@ -23,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/ipc"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
@@ -73,7 +74,7 @@ func (t *Task) contextValue(key interface{}, isTaskGoroutine bool) interface{} {
 			defer t.mu.Unlock()
 		}
 		return t.utsns
-	case CtxIPCNamespace:
+	case ipc.CtxIPCNamespace:
 		if !isTaskGoroutine {
 			t.mu.Lock()
 			defer t.mu.Unlock()
diff --git a/pkg/sentry/syscalls/linux/vfs2/BUILD b/pkg/sentry/syscalls/linux/vfs2/BUILD
index 1e3bd2a50..4a03008f8 100644
--- a/pkg/sentry/syscalls/linux/vfs2/BUILD
+++ b/pkg/sentry/syscalls/linux/vfs2/BUILD
@@ -19,6 +19,7 @@ go_library(
         "memfd.go",
         "mmap.go",
         "mount.go",
+        "mq.go",
         "path.go",
         "pipe.go",
         "poll.go",
@@ -59,6 +60,7 @@ go_library(
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/fasync",
+        "//pkg/sentry/kernel/mq",
         "//pkg/sentry/kernel/pipe",
         "//pkg/sentry/kernel/time",
         "//pkg/sentry/limits",
diff --git a/pkg/sentry/syscalls/linux/vfs2/mq.go b/pkg/sentry/syscalls/linux/vfs2/mq.go
new file mode 100644
index 000000000..d5d81c6e2
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/mq.go
@@ -0,0 +1,98 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vfs2
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/mq"
+)
+
+// MqOpen implements mq_open(2).
+func MqOpen(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	nameAddr := args[0].Pointer()
+	flag := args[1].Int()
+	mode := args[2].ModeT()
+	attrAddr := args[3].Pointer()
+
+	name, err := t.CopyInString(nameAddr, mq.MaxName)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	rOnly := flag&linux.O_RDONLY == linux.O_RDONLY
+	wOnly := flag&linux.O_WRONLY == linux.O_WRONLY
+	readWrite := flag&linux.O_RDWR == linux.O_RDWR
+
+	create := flag&linux.O_CREAT == linux.O_CREAT
+	exclusive := flag&linux.O_EXCL == linux.O_EXCL
+	block := flag&linux.O_NONBLOCK != linux.O_NONBLOCK
+
+	var attr linux.MqAttr
+	var attrPtr *linux.MqAttr
+	if attrAddr != 0 {
+		if _, err := attr.CopyIn(t, attrAddr); err != nil {
+			return 0, nil, err
+		}
+		attrPtr = &attr
+	}
+
+	opts := openOpts(name, rOnly, wOnly, readWrite, create, exclusive, block)
+
+	r := t.IPCNamespace().PosixQueues()
+	queue, err := r.FindOrCreate(t, opts, linux.FileMode(mode), attrPtr)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	fd, err := t.NewFDFromVFS2(0, queue, kernel.FDFlags{
+		CloseOnExec: flag&linux.O_CLOEXEC != 0,
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+	return uintptr(fd), nil, nil
+}
+
+// MqUnlink implements mq_unlink(2).
+func MqUnlink(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	nameAddr := args[0].Pointer()
+	name, err := t.CopyInString(nameAddr, mq.MaxName)
+	if err != nil {
+		return 0, nil, err
+	}
+	return 0, nil, t.IPCNamespace().PosixQueues().Remove(t, name)
+}
+
+func openOpts(name string, rOnly, wOnly, readWrite, create, exclusive, block bool) mq.OpenOpts {
+	var access mq.AccessType
+	switch {
+	case readWrite:
+		access = mq.ReadWrite
+	case wOnly:
+		access = mq.WriteOnly
+	case rOnly:
+		access = mq.ReadOnly
+	}
+
+	return mq.OpenOpts{
+		Name:      name,
+		Access:    access,
+		Create:    create,
+		Exclusive: exclusive,
+		Block:     block,
+	}
+}
diff --git a/pkg/sentry/syscalls/linux/vfs2/vfs2.go b/pkg/sentry/syscalls/linux/vfs2/vfs2.go
index 0fc81e694..4eb15a7f2 100644
--- a/pkg/sentry/syscalls/linux/vfs2/vfs2.go
+++ b/pkg/sentry/syscalls/linux/vfs2/vfs2.go
@@ -112,6 +112,8 @@ func Override() {
 	s.Table[232] = syscalls.Supported("epoll_wait", EpollWait)
 	s.Table[233] = syscalls.Supported("epoll_ctl", EpollCtl)
 	s.Table[235] = syscalls.Supported("utimes", Utimes)
+	s.Table[240] = syscalls.Supported("mq_open", MqOpen)
+	s.Table[241] = syscalls.Supported("mq_unlink", MqUnlink)
 	s.Table[253] = syscalls.PartiallySupported("inotify_init", InotifyInit, "inotify events are only available inside the sandbox.", nil)
 	s.Table[254] = syscalls.PartiallySupported("inotify_add_watch", InotifyAddWatch, "inotify events are only available inside the sandbox.", nil)
 	s.Table[255] = syscalls.PartiallySupported("inotify_rm_watch", InotifyRmWatch, "inotify events are only available inside the sandbox.", nil)
@@ -241,6 +243,8 @@ func Override() {
 	s.Table[86] = syscalls.Supported("timerfd_settime", TimerfdSettime)
 	s.Table[87] = syscalls.Supported("timerfd_gettime", TimerfdGettime)
 	s.Table[88] = syscalls.Supported("utimensat", Utimensat)
+	s.Table[180] = syscalls.Supported("mq_open", MqOpen)
+	s.Table[181] = syscalls.Supported("mq_unlink", MqUnlink)
 	s.Table[198] = syscalls.Supported("socket", Socket)
 	s.Table[199] = syscalls.Supported("socketpair", SocketPair)
 	s.Table[200] = syscalls.Supported("bind", Bind)
@@ -271,6 +275,5 @@ func Override() {
 	s.Table[287] = syscalls.Supported("pwritev2", Pwritev2)
 	s.Table[291] = syscalls.Supported("statx", Statx)
 	s.Table[441] = syscalls.Supported("epoll_pwait2", EpollPwait2)
-
 	s.Init()
 }